Technical teams frequently struggle to keep software architecture diagrams synchronized with evolving codebases and documentation repositories. Atlantis Diagrams delivers a unified self-hosted workspace that couples code-driven Mermaid.js diagramming with structured Markdown knowledge bases in a responsive web interface. Engineers can compose flowcharts, sequence diagrams, state machines, entity-relationship models, and Gantt schedules using split-view CodeMirror editors with real-time SVG rendering. An integrated version history tracker automatically captures revision checkpoints across the last 15 document states, letting authors compare modifications and restore previous iterations without data loss. The linked notes environment supports rich Markdown editing, LaTeX mathematical formulas, interactive task checklists, tag indexing, and full-text keyword searches across personal documentation libraries. Canvas controls allow users to pan, zoom, inspect individual nodes, and export finalized graphics directly into vector SVG, high-resolution PNG, or printable PDF documents. Storage engines adapt to deployment scale, running on zero-configuration SQLite databases out of the box with optional PostgreSQL, MySQL, and Redis caching layers for high-concurrency environments. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.